Suspension fork for a bicycle

ABSTRACT

A suspension fork for a bicycle includes at least one stanchion tube and at least one slider tube interacting therewith and a wheel receiving space adjacent thereto. The suspension fork includes a damper system with a damper chamber divided into a first chamber and a second chamber by a movable piston. The suspension fork further includes a damping device for the rebound stage and a damping device for the compression stage are provided. A shut-off valve is provided for selectively locking the rebound stage. The damper chamber comprises a connecting duct with a flow damper that connects the second chamber with the first chamber when the stanchion tube and the slider tube interacting therewith are compressed more than a predefined distance such that in the case of a forceful compression and with the shut-off valve of the rebound stage activated, slow decompression is allowed up to a damper position as defined by the predetermined distance.

BACKGROUND

The present invention relates to a suspension fork for a bicycle.

Employing suspension forks in bicycles has basically been known for along time. Suspension forks configured in particular as telescopicsuspension forks are installed in downhill and mountain bikes and incross-country bikes, and increasingly in everyday bicycles as well.

Most suspension forks comprise a pair of tubes stationary that arerelative to the bicycle frame, the so-called stanchion tubes, and twolower, movable tubes, the so-called slider tubes, to which the wheel hubis fastened. The stanchion tubes may be held together by means of a forkbridge or fork crown at the center of which the fork column is attachedas a rule. Most slider tubes or outer tubes are larger in diameter so asto accommodate the stanchion tubes to be slidingly displaceable in theslider tubes.

The riders of suspension fork-equipped bicycles desire suspension forkswhose springing and damping characteristics can be easily and quicklyadjusted to speedily adapt the current suspension fork characteristicsto actual ambient conditions.

When the cyclist rides up a steep hill or a steep incline it isadvantageous if the suspension fork compresses such that the inclinationangle of the rider or the bicycle is reduced. This enables the rider tomove the overall center of gravity forward such that the feeling or therisk of a backwards roll-over is reduced.

To achieve compression of the suspension fork and prohibit subsequentdecompression, it is possible in known suspension forks to activate ashut-off valve for locking the rebound stage so as to lock the fluidpath in the rebound stage. Subsequently only compressing is enableduntil the suspension fork has reached the maximum compressed state. Bylocking the rebound stage, rebound is effectively prevented.

By way of such activating of the shut-off valve for the rebound stage,the angle of the bicycle on a steep inline is effectively reduced. Thereis the drawback, however, that complete compression will also cause thetrail angle and the steering angle to change greatly.

Against the background of the described prior art it is therefore theobject of the present invention to provide a suspension fork allowing adefined compression of the suspension fork in steep uphill grades.

SUMMARY

The suspension fork according to the invention is provided to be usedwith a bicycle and comprises at least one stanchion tube and at leastone slider tube interacting therewith and a wheel receiving spaceadjacent thereto. A damper system is provided with a damper chamberdivided into a first chamber and a second chamber by means of a movablepiston.

Furthermore, the suspension fork comprises a damping device for therebound stage and at least one damping device for the compression stage.At least one shut-off valve is provided for selectively locking therebound stage. The damper chamber comprises at least one connecting ductwith a flow damper that connects the second chamber with the firstchamber external of the movable piston when the stanchion tube and theslider tube interacting therewith are compressed by more than apredefined distance such that in the case of a forceful compression andwith the shut-off valve of the rebound stage activated, slowdecompression is allowed up to a damper position as defined by thepredetermined distance.

The suspension fork according to the invention has many advantages. Itis a considerable advantage of the suspension fork according to theinvention that for rides uphill and steep inclines and otherapplications a defined compression of the suspension fork is allowedwithout which the suspension fork compresses entirely. Due to theconnecting duct that opens as a predetermined compression is exceeded,fluid compensation may occur even if the shut-off valve for the reboundstage is activated.

Another considerable advantage is that the flow damper in the connectingduct only allows slow fluid compensation of the damping fluid such thatrebound occurs slowly. In this way, it is ensured that in normaloperation the connecting duct only slightly influences the springing anddamping characteristics of the damping device for the rebound stage evenin the case of forceful compression. In normal operation, the user doesnot become aware of compression occurring beyond the predetermineddistance. Changes in the springing and damping characteristics virtuallydo not occur. Therefore the flow damper is dimensioned accordingly so asto provide slow decompression.

A considerable advantage of the suspension fork according to theinvention is that independently of the weight of the rider thesuspension fork will always be set in the same position even in the caseof a locked rebound stage. This position is independent from the actingforces and it is only defined by the position of the connecting duct.This is very advantageous since in this way the same position is set forevery rider which is very advantageous in particular in steep uphillrides.

Preferably, the flow cross-section of the flow damper of the connectingduct is smaller than half the maximum flow cross-section of the dampingdevice for the compression stage.

Particularly preferably, the ratio of the flow cross-section of the flowdamper to the maximum flow cross-section of the damping device for thecompression stage is smaller than 1:5 and in particular smaller than1:10 and particularly preferably smaller than 1:20.

Particularly preferably, the ratio of the flow cross-sections of theflow damper to the maximum flow cross-section of the damping device issmaller than 1:10 or 1:20 or even 1:30.

For example when the maximum flow cross-section of the damping devicefor the compression stage is 3 or 4 mm, then a diameter of the flowdamper may for example be 0.5 mm or 1 mm or 1.5 mm. Due to the quadraticeffect on the area, ratios between approximately 1:64 and 1:10 ensue.Larger and smaller ratios are also possible.

By way of the considerable difference between the flow cross-sections ofthe flow damper of the connecting duct and the maximum flowcross-section of the damping device, it is ensured that even in the caseof a compression beyond the predetermined distance any changes in thedamping properties of the suspension fork can virtually not be sensed.

Preferably, at least one damping device is configured as an adjustabledamper valve and in particular as a low-speed damper valve. In this way,the damping characteristics in the rebound stage and in the compressionstage can be adjusted accordingly.

Advantageously, a fixedly set high-speed damper valve is provided forrebound damping and/or compression damping to enlarge the cross-sectionfor the damping fluid in the case of heavy impacts or shocks so as toprovide kind of an adequate damping.

Preferred specific embodiments also provide a shut-off valve for thecompression stage. By way of simultaneously activating a shut-off valvefor the compression stage and a shut-off valve for the rebound stage,the suspension fork is virtually set rigid.

Preferably, the connecting duct comprises at least one overflowaperture, a duct or an annular gap, and an aperture. Preferably, theconnecting duct is provided external of the damper chamber. Saidoverflow aperture connects the damper chamber with the duct or annulargap. An annular gap as the duct may for example extend around the damperchamber. The aperture in turn connects the connecting duct with thedamper chamber at the end where the first chamber is disposed.

Now, when the movable piston is located between the aperture and theoverflow aperture, then the connecting duct connects the first chamberwith the second chamber so as to allow exchange of fluid.

Such exchange of fluids takes place slowly since a flow damper isprovided in the connecting duct. The flow damper may be formed by one ormore overflow apertures but it may as well be provided at the apertureat the other end of the connecting duct or else formed by the connectingduct per se. For example, the duct may be suitably small incross-section so as to allow only slow exchange of damping fluid betweenthe first chamber and the second chamber even if the connecting ductconnects the first chamber with the second chamber.

Preferably, the duct or the annular gap is limited inwardly by means ofan inner tube and outwardly, by means of a center tube. Said center tubeis positioned inside the stanchion tube.

In preferred more specific embodiments, the connecting duct can be shutoff. For example, a shut-off valve may be provided to shut off theconnecting duct by way of external control.

Advantageously, the at least one slider tube is provided to be lockedtowards the stanchion tube in any desired compressed position beneaththe damper position defined by the predetermined distance. This mayoccur for example by way of activating both the shut-off valve for therebound stage and the shut-off valve for the compression stage. If thedamper position is so as to not exceed the predetermined distance ofcompressing, then a rigid suspension fork is provided in this position.Only when compression exceeds the predetermined distance can exchange ofdamping fluid take place through the connecting duct such that over timethe damping position approximates the defined damper position.

In advantageous more specific embodiments, the predetermined distanceamounts to between approximately 20 percent and 50 percent of themaximum spring travel. This allows to achieve an advantageous positionof the suspension fork in which the inclination angle of the bicycle isconsiderably reduced which may be advantageous in riding uphill.

In preferred more specific embodiments, the damper system comprises acontrol section at and in particular inside a stanchion tube whichcontrol section is positioned above the first chamber and the firstchamber is positioned above the second chamber. By way of a dampersystem positioned at or in the vicinity of the upper end of thestanchion tube, a simple structure of the suspension fork according tothe invention is possible since the positioning of the damping deviceand the shut-off valves at the control section allows easy accessibilityof each of the valves. In this way, the control section may be providedwith all of the adjusting elements which may be operated by the riderduring a ride if and as required.

Preferably, a joint adjusting element is provided with which to adjustor activate the shut-off valve of the rebound stage and the shut-offvalve of the compression stage. Preferably, the joint adjusting elementis positioned at the slider tube or the fork crown where it is inparticular pivotally attached. This allows the rider to bend forwardlyduring a ride and to actuate the joint adjusting element at thestanchion tube or the fork crown to carry out the desired adjustments.

Optionally, the joint adjusting element may be provided to be remotelycontrolled, being operated by means of an electric control element or alever at the handlebar or the like.

For all of the configurations, it is particularly preferred for themovable piston to be connected with the slider tube via a piston rodwherein the slider tube is in particular provided with the dropout toreceive a wheel.

The slider tube or slider tubes and the stanchion tube or stanchiontubes may consist of a metal and in particular a light metal. It is alsopossible to employ fibrous composite materials. In a specificembodiment, the stanchion tubes consist of metal at least in part andthe slider tubes consist of a fibrous composite material at least inpart. This allows a design both sturdy and lightweight.

In all the configurations, the suspension fork is preferably configuredin right-side-up structure in which two stanchion tubes affixed on thefork bridge of the suspension fork are provided which plunge into twocorresponding larger-diameter slider tubes. Employing with othersuspension forks according to a different construction principle ispossible as well.

In all the configurations and more specific embodiments, the slidertubes are preferably provided for a sliding contact with the stanchiontubes of the suspension fork. Preferably, the stanchion tubes aresupported in the slider tubes by means of slide bearings.

Preferably, the lower end of at least one slider tube is provided with awheel receiving device or a dropout which is in particular provided toreceive a wheel.

It may also be employed with one stanchion tube and one slider tubeonly.

Preferably, the lower end of at least one slider tube is provided with adropout which is in particular provided to receive a wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and applications of the present invention ensue fromthe description of exemplary embodiments which will now be discussedwith reference to the enclosed figures.

FIG. 1 is a front view of a suspension fork according to the invention;

FIG. 2 is a cut side view along A-A of the suspension fork in FIG. 1;

FIG. 3 is an enlarged, cut side view of the suspension fork in thecompression stage;

FIG. 4 is a cut side view of the suspension fork in the rebound stage;

FIG. 5 is an enlarged view of the control section of the damper systemof the suspension fork in FIG. 3 in the compression stage;

FIG. 6 is an enlarged view of the control section of the damper systemof the suspension fork in FIG. 4 in the rebound stage;

FIG. 7 is the control section of the damper system of the suspensionfork in FIG. 1 with the adjusting lever in the first shift stage;

FIG. 8 is the control section of the damper system of the suspensionfork in FIG. 1 with the adjusting lever in the second shift stage;

FIG. 9 is an enlarged cross-section of a stanchion tube in the upperregion;

FIG. 10 is an enlarged cross-section of a stanchion tube in the regionof the overflow aperture;

FIG. 11 is the suspension fork of FIG. 1 with the rebound stage lockedin compressing;

FIG. 12 is the suspension fork of FIG. 1 with the rebound stage lockedafter intense compression;

FIG. 13 is the suspension fork of FIG. 1 with the rebound stage lockedand subsequent slow decompression;

FIG. 14 is an enlarged illustration of a cross-section of the controlsection of another suspension fork;

FIG. 15 is another cross-section of the control section of thesuspension fork according to FIG. 14; and

FIG. 16 is an enlarged cross-section of the suspension fork according toFIG. 14 with the movable piston.

DETAILED DESCRIPTION

In FIGS. 1 to 13, a first embodiment of the suspension fork 1 accordingto the invention is illustrated in views some of which are highlyschematic. For better clarity and to better explain the function, someparts and components have been omitted.

The suspension fork 1 illustrated in FIG. 1 comprises in its upperregion a fork column 26 that is centrally attached to a connector 7configured as a fork crown 27 to rotatably attach the fork to thebicycle frame.

The two ends of the fork crown 27 respectively have stanchion tubes 2and 3 affixed to the fork crown 27. A damper system 8 is disposed instanchion tube 2 and a suspension system 50 is provided in stanchiontube 3. It is also conceivable to incorporate the damper system 8 andalso the suspension system 50 in a stanchion tube 2 or 3. By means ofthe damper system 8 and the suspension system 50, the suspension fork 1is provided with the desired springing and damping properties.

A slider tube unit is displaceably provided at the stanchion tubes 2 and3, comprising slider tubes 4 and 5 connected with one another through atleast one connecting bracket 56. The slider tube unit may consist ofseveral component parts but it may as well be manufactured integrally.

A wheel receiving space 6 is provided between the pair of slider tubes 4and 5 or between the stanchion tubes 2 and 3. A wheel, presently notshown, may be attached to the dropouts 18 and 19 of the slider tubes 4and 5 at the lower end 17 of the suspension fork 1.

At the upper end 16 a damper system 8 is incorporated in the stanchiontube 2, as illustrated in FIG. 2.

The damper system 8 comprises a damper chamber 10 divided into an upper,first chamber 11 and a lower, second chamber 12 by means of a movablepiston 9. Above the damper chamber 10, a control section 15 is providedwhich concurrently forms the top end of the damper chamber 10. Themovable piston 9 is presently configured as a closed pump plunger whereflow through the movable piston 9 is not possible. When the piston ismoved, external return flow must occur from the upper or first damperchamber 11 to the lower or second damper chamber 12.

While the damper chamber 10 with the first chamber 11 and the secondchamber 12 are configured as a high pressure chamber 29, the controlsection 15 is provided with a low pressure chamber 32.

A damping device 57 for rebound damping and a damping device 58 forcompression damping are provided in the control section 15. Presently,the damping device 57 is provided as an adjustable damper valve 13 foradjusting the rebound stage damping. The damping device 58 is providedas an adjustable damper valve 14 for adjusting the compression stagedamping. Furthermore, the suspension fork includes a shut-off valve 24for the rebound stage, a shut-off valve 25 for the compression stage,and high-speed damper valves 22, 23 for the rebound stage and thecompression stage and a blow-off valve 48.

At the upper end of the first chamber 11 of the damper chamber, a checkvalve 51 is provided which by means of a spring (not shown) is preloadedin a closed position in which the check valve 51 closes the direct flowconnection with the low pressure chamber 32. The check valve 51 opens asthe first chamber has a relative negative pressure in the rebound stage(see FIG. 6).

A check valve 52 is provided which is preloaded in closed position bymeans of a spring that is not shown in detail. The check valve 52 opensas the second chamber 12 has a relative negative pressure in thecompression stage (see FIG. 5) and the damping fluid is sucked from thelow pressure chamber 32 through the return channel 35 and the externalchamber 31 into the second chamber 12.

In the rebound stage, the damping medium supplied to the riser 34 fromthe return channel 35 is introduced into the low pressure chamber 32through the damper valve 13. In the case of the compression stage, thedamping medium introduced into the duct riser 33 from the first chamber11 is introduced into the low pressure chamber 32 through the dampervalve 14. Then in the compression stage, the damping fluid enters fromthe first chamber 11, which forms part of the internal chamber 30,through the riser 33 into the control section 15. Depending on theposition of the damper valve 14 and after application of a load, thedamping fluid is introduced through the damper valve 14 and/or throughthe high-speed damper valve 23 into the low pressure chamber 32.

In the case of the rebound stage, the damping fluid enters from thesecond chamber 12 in the lower region of the damper system 8 into theexternal chamber 31 which is configured as a high pressure chamber andconfined in the lower region 36 of the second chamber 12 by the externalwall of the stanchion tube 2 and by a center tube 37 which radiallyencloses the stanchion tube 2 in the lower region 36 of the secondchamber 12. In this way, a thermal insulation is achieved from theslider tube 4 which encloses the stanchion tube 2 in the lower region 36of the second chamber 12 so as to largely prevent the slider tube 4 fromheating in the lower region.

In relation to the loads occurring, the movable piston 9 slides upwardlyand downwardly inside the damper chamber 10 wherein radially outwardlysealing against the internal chamber 30 occurs through a seal 49.

The damper valves 13 and 14 in the present embodiment are disposeddisplaceably via adjusting elements 21. The adjusting elements 21 may beconfigured as screw heads 28 wherein rotating the adjusting element 21inserts the respective damper valve 13 or 14 further into the top endwall of the control section 15. In this way, slots or radial bores 54and/or 55 through which the damping oil is directed in the compressionstage or the rebound stage, are widened or narrowed. In this way, viarotational movement of the adjusting elements 21 of the damper valves 13and 14, an efficient adjustment of the damping effect of the reboundstage and the compression stage is possible separate from one another.This adjustment of the damping effect occurs for normal operation inwhich the suspension fork is adjusted for damping small, medium or heavyimpacts.

To ensure damping including in the case of particularly heavy impacts,the high-speed damper valves 22 and 23 are provided for the reboundstage or the compression stage respectively. Although the high-speeddamper valves 22 and 23 are as a rule not provided to be adjustable,this is possible as well.

In the present embodiment, preloading devices are provided which are forexample configured as coil springs so as to preload the respectivehigh-speed damper valves 22 and 23 in the closed position. Now, asparticularly large impacts occur the pressure in the damper chamberrises correspondingly such that the force of the respective preloadingdevices is overcome and the respective high-speed damper valve 22 or 23opens. This will cause the valves to open in the case of sufficientlyforceful loads.

FIG. 3 shows compressing in the compression stage while FIG. 5 shows thepositions of each of the valves in enlarged illustration. FIG. 4 showsdecompressing in the rebound stage while FIG. 6 shows enlargedillustrations of the valve positions.

It can clearly be seen in FIGS. 3 to 6 that both the shut-off valves 24and 25 are open while the damper valves 13 and 14 are illustrated openor closed, depending on the operating condition.

As can in particular be taken from the illustration in FIG. 3, anoverflow aperture 45 is located at the distance 46 from the lower end ofthe damper chamber 10 so as to allow the damping fluid to exit from thesecond chamber 12 even if the shut-off valve 24 for the rebound stage isclosed until the piston 9 closes the overflow aperture 45, presentlyfrom above.

The shut-off valves 24 and 25 for the rebound stage and the compressionstage serve to selectively prohibit damping in the rebound stage or inthe compression stage. Damping may be prohibited by activating either ofthe valves such that the flow passage either for the rebound stage orthe compression stage closes.

It is a considerable advantage of the illustrated embodiment that onesingle adjusting lever 40 is provided as the adjusting element 21 withwhich to intentionally and selectively jointly activate both theshut-off valve 24 of the rebound stage and the shut-off valve 25 of thecompression stage.

To this end, the adjusting lever 40 is pivotally disposed at the upperend 16 of the control section 15 such that the adjusting lever 40presently projects from the upper end of the stanchion tube 2 and can beactuated by the rider while the operator is riding. All the rider needsto do is move one hand down to the fork crown 17 of the fork 1 and thenby way of rotationally moving the adjusting lever 40, he can shiftbetween presently three to four shift stages. In a preferredconfiguration, the adjusting lever 40 may be configured as a remotelycontrolled adjusting element actuated e.g. by a control mechanism at thehandlebar.

In a first setting or first position 41 of the adjusting lever 40 shownin FIG. 5, both the shut-off valve 24 of the rebound stage and theshut-off valve 25 of the compression stage are not activated so as toallow free flow through the valves 24 and 25. This is the standardoperating condition of the suspension fork 1 in which both a rebounddamping and a compression damping and compression and decompression arepossible.

By way of rotational movement of the adjusting lever 40 from the firstposition 41 to the second rotational position 42 as illustrated in FIG.7, the shut-off valve 24 of the rebound stage is activated and thusclosed such that in the rebound stage flow-through is substantiallydisabled. In the compression stage the shut-off valve 25 is still open.This means that compression is still possible while subsequent reboundis prohibited. Such a rotational position 42 of the adjusting lever 40makes sense for example when the rider climbs a steep incline and wishesto reduce the inclination angle of the bicycle. By means of the frontwheel fork compressing, its effective height decreases so that a safeand comfortable riding position is achieved. After activation of thepivot position 42 by the adjusting lever 40 being rotated, every impactand every compression causes the front wheel fork 1 to lower until apre-determined setting is reached.

By way of rotating the adjusting lever 40 further into a third shiftposition 43 illustrated in FIG. 8, both the shut-off valve 24 for therebound stage and the shut-off valve 25 for the compression stage areclosed. Adjusting the adjusting lever 40 in this way is possible at anytime. In this way, both decompression and compression of the fork isprohibited. The suspension fork 1 practically behaves as if nosuspension and damper system are present. Only in the case ofparticularly heavy impacts the blow-off valve 48 can be activated,allowing flow-through so as to limit the maximum pressure occurring inthe system and to prevent the damper system 10 of the suspension forkfrom being damaged or from breaking, for example if the rider jumps withhis bicycle while the adjusting lever is in the third shift position 43.

It may further be possible to shift the adjusting lever 40 to a fourthshift position 44 in which the shut-off valve for the compression stageis closed while the shut-off valve 24 for the rebound stage is open. Inthis way, decompression of the spring is allowed while compression isprohibited.

The suspension fork 1 furthermore comprises the overflow aperture 45indicated above which is provided at a distance 46 from the lower end ofthe first chamber 12. By means of the overflow aperture 45 thesuspension fork 1 is prevented from compressing completely if theshut-off valve 24 of the rebound stage is activated.

A connecting duct 60 is provided in which at least one flow damper 63 isprovided. The connecting duct 60 serves to allow the suspension fork toslowly, automatically rebound back to a specific measure when theshut-off valve 24 of the rebound stage is activated after heavycompressions.

To this end, the connecting duct 60 provides a flow connection for thedamping fluid between the second chamber 12 and the first chamber 11 asthe stanchion tube 2 and the slider tube 4 cooperating therewith havecompressed by more than a specified distance 46. In this way, in thecase of forceful compression and with the shut-off valve 24 of therebound stage activated, slow decompression is allowed up to a damperposition 68 as defined by the predetermined distance 46.

The configuration of the overflow valve or the overflow aperture 45 isillustrated in FIGS. 9 and 10. In the range between approximately 20 and50% of the compression travel at least one overflow aperture 45 isprovided at the damper chamber 10. The overflow aperture 45 is locatedat the distance 46 from the bottom while the maximum stroke correspondsto the length 47. Presently, the at least one overflow aperture 45 isconnected with the aperture 61 via the duct formed as an annular duct 62and presently opens into the riser 33. In this way, damping fluid canimmediately flow from the chamber 12 into the riser 33 and thus returninto the chamber 11. The damping fluid can pass from the chamber 12 viathe overflow aperture 45 into the duct 60 and further through theaperture 61 into the riser 33 and into the first chamber 11 such thatthe suspension fork rebounds until the piston closes the overflowaperture 45 again.

The flow damper 63 is presently formed by the overflow aperture 45 or bythe overflow apertures 45, if several are present. The flowcross-section 64 of the flow damper 63 is formed by the clear passagearea of the overflow aperture 45 (or by the sum of the areas of each ofthe overflow apertures 45). At any rate, the flow cross-section 64 ispresently substantially smaller than half the maximum flow cross-sectionof the damping device 58 or the damper valve 14 for the compressionstage.

The ratio of the flow cross-section 64 of the flow damper 63 to themaximum flow cross-section of the damping device 58 for the compressionstage is in particular smaller than 1:3 and preferably smaller than 1:5and particularly preferably smaller than 1:8. Values of 1:10 or 1:20 andin particular 1:30 are conceivable and preferred. The area is inparticular dimensioned such that the connecting duct 60 when open onlyslightly influences the damping reaction of the suspension fork.

The same preferably applies to the ratio of the flow cross-section 64 ofthe flow damper 63 to the maximum flow cross-section of the dampingdevice 50 for the rebound stage.

The annular gap 62 is confined by an internal tube 65 and a center tube66 both of which are positioned concentrically inside the stanchiontube.

In other configurations, the connecting duct can be shut off e.g. via acontrollable valve.

In other configurations, the duct 60 may open immediately into the lowpressure chamber 32 through an aperture 61 (variant not illustrated).Thus, a suspension fork can be adjusted to different operational modes.For example, the suspension fork may be adjusted to be entirely rigid orcompressed a specific amount e.g. for riding up-hill.

The function and mode of operation of the overflow valve 45 will now beexplained with reference to FIGS. 11 to 13.

In the illustration of FIG. 11 the suspension fork 1 is in the reboundstate with the shut-off valve 24 of the rebound stage activated to allowthe suspension fork 1 to compress while rebound is substantiallyprohibited.

After activating the shut-off valve 24 by displacing the adjusting lever40 to the second shift position 42, the riser 34 is closed for therebound stage. The impacts occurring during the ride cause thesuspension fork 1 to lower until the suspension fork has reached, forexample, the position shown in FIG. 13 in which the piston 9 iscompressed down to the overflow aperture 45.

Now, when another heavy impact acts on the suspension fork 1 in thisposition, the suspension fork is compressed further beyond the overflowaperture 45 (see FIG. 12). Thus, the overflow aperture 45 is opened suchthat the locking action of the shut-off valve 24 is bypassed. Theconnecting duct 60 connects the second chamber 12 with the first chamber11 and the suspension fork is automatically slowly lowered. The exchangeof the damping fluid occurs slowly because the flow cross-section 64 ofthe overflow aperture 45 serving as the flow damper 63 is small.

The overflow aperture 45 enables the suspension fork 1 to rebound backuntil the condition shown in FIG. 13 is achieved in which the overflowaperture 45 is closed again.

On the whole, a system is provided by means of the overflow aperture 45,the activated shut-off valve 24 notwithstanding, so as to limit thesuspension travel even if the shut-off valve 24 of the rebound stage isactivated. By way of disposing the overflow aperture 45, the desiredsuspension travel can be adjusted.

In this way, a function is provided which in up-hill rides provides therequired compression while on the other hand a small damping functioncontinues to be available.

With several adjustable or shiftable overflow apertures 45 provided atdifferent heights, the suspension travel still available with theshut-off valve 24 activated can be adjusted correspondingly.

FIGS. 14 to 16 show cross-sections of another embodiment of a suspensionfork 1 according to the invention. Like or similar parts are providedwith the same reference numerals. The damper system 8 in turn isinserted in a stanchion tube 2 or 3 of a suspension fork 1, as shown inFIG. 1.

Unlike the preceding embodiment, the embodiment according to FIGS. 14 to16 provides for the damper valve 13 to be a low-speed damper valve forthe rebound stage at the top end of the damper chamber 10. The dampervalve 14 as a low-speed damper valve for the compression stage islikewise disposed at the top end of the damper chamber 10. The valvesseparate the high pressure region from the low pressure region. Thecontrol section 15 virtually extends from the upper end of the firstchamber 11 to the upper end 16 of the stanchion tube 2.

The damper valves 13 (low-speed) for the rebound stage and 14(low-speed) for the compression stage are connected with the upper end16 through corresponding control elements or control pins and they areadjustable by way of actuating the adjusting element 40.

In FIG. 14 it can be seen that the control pin 73 acts on the shut-offvalve 24 for the rebound stage such that lockout may be activated asneeded and rebound damping , may be locked. Another control pin 75 actson the shut-off valve 25 for the compression stage and it mayselectively lock compression damping. In the case of particularlyforceful shocks the blow-off valve 48 opens if the shocks generate aforce exceeding the interior force of the spring 74 of the blow-offvalve 48.

The blow-off valve 48 is sealed by means of seals 77 both relative tothe control pin 76 and to the external wall. The high-speed damper valve23 is presently connected in parallel to the low-speed damper valve 14.

Above the shut-off valves 24 and 25, the oil compensation chamber 72 isseparated from a gas volume 79 by means of a partition wall. Thepartition wall is presently configured as a rubber hose 70, ensuringreliable separation of the oil from the gas volume. The gas volume 79 isunder excess pressure of typically between 1 and 5 bar. The movablepiston 9 is presently configured as an impermeable pump plunger. Whenthe movable piston 9 plunges, the volume available to the oil isreduced. In this way the gas volume 79 compresses by means of theflexible rubber hose 70 and the compensation chamber 72 expandscorrespondingly.

The O-ring 71 covers a bore. The O-ring 71 together with the bore servesas a one-way valve and serves for filling up the suspension fork withgas after mounting. The one-way valve opens as the internal pressureexpands the O-ring far enough for gas to exit through the gap generated.

FIG. 15 shows another cross-section of the control section 15 whereinFIG. 15 shows a cross-section approximately transverse to thecross-section according to FIG. 14.

One can see the damper valve 13 as a low-speed control valve for therebound stage. By way of longitudinal adjustment the regulating gap 69is regulated and thus the flow resistance is adjusted.

FIG. 16 shows a cross-section of the region of the piston in the lowerregion of the damper chamber, where as in the preceding embodiment theoverflow aperture 45 is provided.

The piston rod 20 is sealed by way of a seal 77 against the damperchamber 10. At the upper end of the piston rod 20, the movable piston 9is provided that is configured as a pump plunger and that separates thefirst chamber 11 from the second chamber 12.

At its bottom, the second chamber 12 makes a transition to theinterspace 38 connected therewith. The second chamber 12 or thelow-pressure region is limited externally by the center tube 37 that issealed externally by means of a seal 77 towards the stanchion tube. Atits upper end, the interspace 38 is radially outwardly connected withthe external chamber 31 through at least one aperture 78. The secondchamber 12 together with the interspace 38 and the external chamber formthe rebound stage chamber.

Positioned radially within the external chamber 31, the center tube 66is provided in which the inner tube 65 is positioned concentrically.Between the inner tube 65 and the center tube 66 a duct 60 is provided.From the duct 60, an aperture 61 opens into the first chamber 11 in anupper region and an aperture 45 into the damper chamber 10, in a lowerregion. In this way, the duct 60 acts as a bypass between the firstchamber 11 and the second chamber 12 when the movable piston 9 islocated between the apertures 45 and 61. In this way, compensation ispossible even in the case of a locked damping. Compensation occursslowly since the flow cross-sections of the apertures are intentionallysmall.

To still further reduce the flow-through quantities through the overflowapertures 45 and 61, O-rings 71 may be provided across the overflowapertures 45 and 61. In this way, a specific pressure must first beovercome which further slows down the flow and thus inhibits normalfunction as little as possible. It has been shown that the overflowapertures 45 and 61 ought to be very small. And even in the case ofsmall apertures, it makes sense to further reduce flow-through.

Another considerable advantage of the overflow apertures 45 and 61 andthe bypass thus provided is that independently of the weight of therider the same position will always be adjusted even in the case of alocked rebound stage. This position is independent of the acting forcesand it is defined by the position of the bore. This is very advantageoussince in this way the same position is set for every rider which is veryadvantageous in particular in steep uphill rides.

The function will now be described briefly: In the compression stage,i.e. during compression and with the shut-off valves 24 and 25 opened.

Following a shock, the movable piston 9 configured as a pump plungermoves upwardly and the pressure in the first chamber 11 above the piston9 increases. Then the oil will flow upwardly through the damper valve 14(compression stage valve low-speed).

The damper valve 23 is preloaded by a spring such that in the case ofsmall loads a shim seals the damper valve 23. From a specific load orfrom a corresponding excess pressure onwards, the high-speed dampervalve 23 of the compression stage opens such that the damper valves 14and 23 are opened in parallel. The oil flows upwardly into the oilcompensation chamber 72 at the upper end of the stanchion tube. The oilcompensation chamber 72 configured as an annular chamber is formedbetween the stanchion tube wall and the flexible rubber hose 70. Therubber hose 70 compresses by way of the oil flowing into the oilcompensation chamber 72. In the interior of the rubber hose 70, a gasvolume 79 is present. The gas volume 79 is presently filled with air andin the present case under a pressure of e.g. 3-4 bar. In this way, anycavitation in the flowing oil is avoided. By way of the rubber hose andthe gas volume, the volume of the piston rod is compensated. And, forthermal expansion of the oil a suitable reservoir is provided.

During compressing, the pressure concurrently decreases in the secondchamber 12 below the movable piston 9. At its bottom the second chamberis in flow connection with the interspace 38 and the external chamber31, from where oil is now drawn. The external chamber 31 abuts thecontrol section 15. A return flow valve opens there and oil flows out ofthe oil compensation chamber 72 from above.

In rebounding in the rebound stage, the movable piston 9 movesdownwardly and excess pressure forms in the lower, second chamber 12 andthus also in the external chamber 31 while negative pressure forms inthe first chamber 11 above the piston 9.

By way of the negative pressure in the first chamber 11, at least onecheck valve positioned at the upper end opens, and oil is drawn fromabove from the oil compensation chamber 72.

On the whole, the suspension fork 1 according to the invention providesa system which allows high heat dissipation in the upper region of thestanchion tubes 2, 3 wherein all the operating elements 21, 40 can beflexibly arranged in an upper region 16 of the stanchion tubes 2 and 3.

In all the embodiments at least one shut-off valve 24 or 25 and/or atleast one damper valve 13 or 14 may be actuated or activatedelectrically or magnetically. A remotely controlled construction is inparticular possible and preferred. Operating is e.g. possible from thehandlebar. A mechanical remote control is also preferred.

Furthermore the damper valves 13, 14, 22-25 are also located in theupper region 16 of the stanchion tubes 2 or 3 and via a shared adjustinglever 40 provided at the fork crown 27 or at the stanchion tube 2, 3,both a rebound stage lockout (locked rebound stage shut-off valve) and acompression stage lockout (locked compression stage shut-off valve) maybe set such that the fork 1 is rigid both in the compressing directionand in the decompressing direction. At the same time a damping functioncan be ensured via an overflow valve 45 even with the rebound stagelockout activated.

1. A suspension fork for a bicycle, comprising: at least one stanchiontube and at least one slider tube interacting therewith and a wheelreceiving space adjacent said at least one stanchion tube and said atleast one slider tube, said at least one stanchion tube including adamper system having a damper chamber divided into a first chamber and asecond chamber by a movable piston, wherein at least one damping devicefor a rebound stage, at least one damping device for a compression stageand at least one shut-off valve for selectively locking the reboundstage are provided, wherein the damper chamber comprises at least oneconnecting duct with a flow damper that connects the second chamber withthe first chamber external of the piston when the stanchion tube and theslider tube interacting therewith are compressed by more than apredetermined distance such that in the case of a forceful compressionand with the shut-off valve of the rebound stage activated, slowdecompression is allowed up to a damper position as defined by thepredetermined distance.
 2. The suspension fork according to claim 1,wherein a ratio of a flow cross-section of the flow damper to a maximumflow cross-section of the damping device for the compression stage isless than 1:5.
 3. The suspension fork according to claim 1, wherein saidat least one damping device is an adjustable damper valve.
 4. Thesuspension fork according to claim 1, further comprising a fixedly sethigh-speed damper valve for at least one of rebound damping andcompression damping.
 5. The suspension fork according to claim 1,further comprising a shut-off valve for the compression stage.
 6. Thesuspension fork according to claim 1, wherein the connecting ductcomprises at least one of an overflow aperture, a duct or an annular gapand an aperture.
 7. The suspension fork according to claim 6, whereinsaid duct or said annular gap is confined by an internal tube and acenter tube that is disposed inside the stanchion tube.
 8. Thesuspension fork according to claim 1, wherein said at least oneconnecting duct can be shut off at least in one direction.
 9. Thesuspension fork according to claim 1, wherein said at least one slidertube is locked relative to the stanchion tube in any desired compressedposition beneath the damper position defined by the predetermineddistance.
 10. The suspension fork according to claim 1, wherein thepredetermined distance is between 20% and 50% of a maximum springtravel.
 11. The suspension fork according to claim 1, wherein the dampersystem comprises a control section at a stanchion tube wherein thecontrol section is positioned above said first chamber.
 12. Thesuspension fork according to claim 1, further comprising a jointadjusting element wherein by way of the joint adjusting element, theshut-off valve of the rebound stage and a shut-off valve of thecompression stage are each adjustable.
 13. The suspension fork accordingto claim 12, further comprising a fork crown, wherein said jointadjusting element is pivotally attached to said at least one stanchiontube or to said-fork crown.
 14. The suspension fork according to claim1, wherein at least one of said at least one shut-off valve and said atleast one damper are controlled remotely by electrical actuation ormagnetic actuation.
 15. The suspension fork according to claim 1,wherein at least a part of said at least one slider tube consists of afibrous composite material and at least a part of said at least onestanchion tube consists of metal.